KIPUTZ IX: A UNIQUE ASSEMBLAGE OF STEPPE BISON (BISON PRISCUS BOJANUS, 1827) REMAINS FROM THE UPPER PLEISTOCENE OF THE IBERIAN PENINSULA. Kiputz IX is an upper Pleistocene site that has provided the richest set of steppe bison remains in the Iberian Peninsula. This paper provides a metric study of the postcranial skeleton of 18 individuals that conform this tafocenosis. The comparison with other European sets, near in space and time, allows the attribution of this material to the subspecies Bison priscus mediator Hilzheimer. The robustness index of the metacarpus diaphysis indicates the existence of a clear sexual dimorphism and a balance between sexes within the sample. The stage of dental substitution makes evident that the sample is dominated by juvenile and subadult specimens, with a low proportion of adult individuals. The absolute chronology of the remains and its association with an important sample of reindeer confirm that the preferential biotope of this species was the steppe. The bison sample from Kiputz IX constitutes a good basis for comparative studies of large bovid populations from middle and upper Pleistocene of Europe.